[ref. ID; 2014]
Uniformly ciliated ovoid body rounded at both poles and slightly reniform. Peristome oval in outline, lying obliquely across the ventral surface of the body. AZM on the left (posterior) and an undulating membrane on the right (anterior) of the oral aperture. A single contractile vacuole. The macronucleus may be oval or elongate with several micronuclei. Most easily confused with Balantidioides which does not have an undulating membrane and with Condylostoma which has a wide triangular peristome and a highly conspicuous undulating membrane.
Quote; Colin R. Curds, Michael A. Gates and David McL. Roberts "British and other freshwater ciliated protozoa Part II Ciliophora: Oligohymenophora and Polyhymenophora" Cambridge University Press, 1983 (ref. ID; 2014)